A system disclosed in Japanese Patent Application Laid-Open Publication No. 2013-86605 is to connect an intake duct and an exhaust duct to a pack case where a plurality of battery cells are accommodated, take air supplied from a cooling fan into inside the case through the intake duct, and discharge air after heat-exchanging with the battery cells through the exhaust duct to outside.
That is, air discharged outside after heat-exchanging will not return to the inside of the case immediately, and new air for cooling the batteries is always be taken into the inside of the case.
Air supplied from the cooling fan flows towards the battery cell after passing through the inside of the intake duct in the system of the Publication No. '605.
Then, air after passing the battery cells is immediately discharged to outside passing through the inside of the exhaust duct.
That is, there is only a small amount of air that contacts case walls that function as heat releasing surfaces to outside in the process of sucking air, passing the battery cell, and discharging air in the Publication No. '605, thus the heat released to outside is insufficient.
Thus, regarding a point of releasing generated heat by the battery effectively to outside the case, sufficient effect is not obtained in the conventional system, and there is room for improvement.